一种提高稳定性和公平性的主动队列管理机制  

Active Queue Management Improving the Stability and Fairness

作　　者：汤德佑[1] 骆嘉伟[2] 张大方[2] 张白妮[2] 

机构地区：[1]华南理工大学计算机科学与工程学院,广州510640 [2]湖南大学计算机与通信学院,长沙410082

出　　处：《计算机研究与发展》2005年第7期1136-1142,共7页Journal of Computer Research and Development

基　　金：国家自然科学基金项目(60273070);湖南省自然科学基金项目(03JJY309)

摘　　要：结合平均队列和负载衡量拥塞,实现选择性丢包,提出早期选择性丢包算法(ESD).ESD采用指数函数计算丢包概率,使丢包概率随拥塞程度增大而指数递增;引入记录活跃连接状态信息的虚队列,并在虚队列上假轮转,以检测发送速率大的连接;区分非响应性连接和响应性连接,挑选丢包的候选连接,拥塞时优先丢弃候选连接在队列头部的数据包.实验结果表明,ESD可提高队列稳定性,降低Web流和RTT较大连接的丢包率,提高连接占用带宽的公平性,缩短应用响应时间.The IRTF has recommended the utilization of random early detection (RED), which uses the average queue length to determine congestion and dropping probabilities and drops packets randomly. But RED is unstable and can't protect traffic from flows that send more than average bandwidth or flows that fail to use end-to-end congestion control when the load is high. In this paper, it is shown a new scheme called early selective drop (ESD) that uses both load and average queue length to determine congestion and packet drop probabilities. The count of dropping probability is implemented by an exponential function. At the same time, ESD uses a virtual queue to record the per-active-flow state information and uses a method called pseudo-round-robin to filter out the candidate connections from those flows that occupy more bandwidth than average bandwidth. ESD distinguishes non-adaptive greedy traffic from adaptive traffic, short-lived flow from long-lived flow, long-RTT flow from short-RTT flow, and punishes non-adaptive flows when the network becomes congested. When it is time to drop a packet, ESD drops the candidate connection's packet in the front of the queue. The simulations demonstrate that ESD improves the stability of the queue and the fairness between different types of flows, decreases packet losses of WEB traffic and long-RTT flows, and reduces the application's response time.

关 键 词：主动队列管理 虚队列 候选连接 早期选择性丢包 

分 类 号：TP393[自动化与计算机技术—计算机应用技术]